Ternary metal halide scintillators

ABSTRACT

Metal halide scintillators are described. More particularly, the scintillators include doped (e.g., europium-doped) ternary metal halides, such as those of the formulas A 2 BX 4  and AB 2 X 5 , wherein A is an alkali metal, such as Li, Na, K, Rb, Cs or any combination thereof; B is an alkali earth metal, such as Be, Mg, Ca, Sr, Ba or any combination thereof; and X is a halide, such as Cl, Br, I, F or any combination thereof. Radiation detectors comprising the novel metal halide scintillators and other ternary metal halides, such as those of the formulas A 2 EuX 4  and AEu 2 X 5 , wherein A is an alkali metal and X is a halide, are also described.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/906,199, filed on Jan. 19, 2016, which is the national stageapplication of PCT International Patent Application No.PCT/US2014/047248, filed on Jul. 18, 2014, which is based on and claimsthe benefit of U.S. Provisional Patent Application Ser. No. 61/856,393,filed Jul. 19, 2013; the disclosures of which are incorporated herein byreference in their entireties.

TECHNICAL FIELD

The presently disclosed subject matter relates to ternary metal halidescintillator materials, such as europium-containing ternary metal halidescintillator materials. The presently disclosed subject matter furtherrelates to radiation detectors comprising the scintillator materials, tomethods of using the scintillator materials to detect radiation, and tomethods of preparing the scintillator materials.

ABBREVIATIONS

-   -   %=percentage    -   ° C.=degrees Celsius    -   μs=microseconds    -   Ba=barium    -   Be=beryllium    -   Br=bromide    -   Ca=calcium    -   Ce=cerium    -   Cl=chloride    -   Cs=cesium    -   cm=centimeter    -   CT=computed tomography    -   Eu=europium    -   F=fluoride    -   g=grams    -   I=iodide    -   In=indium    -   K=potassium    -   Li=lithium    -   LO=light output    -   MeV=megaelectronvolt    -   Mg=magnesium    -   Na=sodium    -   nm=nanometer    -   ns=nanoseconds    -   PET=positron emission tomography    -   ph=photons    -   PL=photoluminescence    -   PMT=photomultiplier tube    -   Pr=praseodymium    -   Rb=rubidium    -   RL=radioluminescence    -   RT=room temperature    -   SPECT=single photon emission computed tomography    -   Sr=strontium    -   Tb=terbium    -   Tl=thallium    -   TL=thermoluminescence    -   Yb=ytterbium

BACKGROUND

Scintillator materials, which emit light pulses in response to impingingradiation, such as X-rays, gamma rays and thermal neutron radiation, areused in detectors that have a wide range of applications in medicalimaging, particle physics, geological exploration, security and otherrelated areas. Considerations in selecting scintillator materialstypically include, but are not limited to, luminosity, decay time, andemission wavelength.

While a variety of scintillator materials have been made, there is acontinuous need for additional scintillator materials, e.g., to meet oneor more particular needs of different applications.

SUMMARY

In some embodiments, the presently disclosed subject matter provides ascintillator material comprising one of Formulas (I), (II), (III), (IV),(V), or (VI): A₂B_((1-y))L_(y)X₄ (I); AB_(2(1-y))L_(2y)X₅ (II);A′_(2(1-y))L′_(2y)BX₄ (III); A′_((1-y))L′_(y)B₂X₅ (IV);A″_(2(1-y))L″_(2y)BX₄ (V); or A″_((1-y))L″_(y)B₂X₅ (VI); wherein:0.0001≦y≦0.5; A is one or more alkali metal; A′ is one or more of thegroup comprising Li, K, Rb, and Cs; A″ is Na or a combination of Na andone or more additional alkali metal; B is one or more alkali earthmetal; L is selected from the group comprising Eu, Ce, Tb, Yb, and Pr;L′ is selected from the group comprising Tl, In, and Na; L″ is selectedfrom the group comprising Tl and In; and X is one or more halide.

In some embodiments, A or A′ is selected from K, Rb, and Cs. In someembodiments, B is selected from Sr and Ba. In some embodiments, X isselected from Cl, Br, and I. In some embodiments, L is Eu and thescintillator material is A₂B_((1-y))Eu_(y)X₄ or AB_(2(1-y))Eu_(2y)X₅. Insome embodiments, 0.01≦y≦0.1. In some embodiments, 0.025≦y≦0.05.

In some embodiments, the scintillator material comprisesA₂B_(0.95)Eu_(0.05)X₄ or AB_(2(0.975))Eu_(2(0.025))X₅. In someembodiments, the scintillator material is selected from the groupcomprising K₂BaI₄:Eu 5%; K₂BaBr₄:Eu 5%; Rb₂BaCl₄:Eu 5%; K₂SrBr₄:Eu 5%;Rb₂BaCl₄:Eu 2.5%; RbSr₂Cl₅:Eu 2.5%; KSr₂Br₅:Eu 2.5%; KBa₂I₅:Eu 2.5%;CsSr₂I₅:Eu 2.5%; RbBa₂Br₅:Eu 2.5%; RbSr₂Br₅:Eu 2.5%; KSr₂I₅:Eu 4%; andKSr₂I₅:Eu 2.5%.

In some embodiments, the presently disclosed subject matter provides aradiation detector comprising a photon detector and a scintillationmaterial, wherein the scintillation material comprises one of Formulas(I), (II), (III), (IV), (V), or (VI). In some embodiments, the detectoris a medical diagnostic device, a device for oil exploration, or adevice for container or baggage scanning. In some embodiments, thepresently disclosed subject matter provides a method of detecting gammarays, X-rays, cosmic rays, and/or particles having an energy of 1 keV orgreater, the method comprising using the radiation detector comprisingthe photon detector and the scintillation material of one of Formulas(I), (II), (III), (IV), (V), or (VI).

In some embodiments, the presently disclosed subject matter provides aradiation detector comprising a photon detector and a scintillationmaterial, wherein the scintillation material comprises one of Formulas(I′), (II′), (III′), (IV′), (V′) or (VI′): A₂B_((1-z))L_(z)X₄ (I′);AB_(2(1-z))L_(2z)X₅ (II′); A′_(2(1-z))L′_(2z)BX₄ (III′);A′_((1-z))L′_(z)B₂X₅ (IV′); A″_(2(1-z))L″_(2z)BX₄ (V′); orA″_((1-z))L″_(z)B₂X₅ (VI′); wherein: 0.0001≦z≦1.0; A is one or morealkali metal; A′ is one or more of the group comprising Li, K, Rb, andCs; A″ is Na or a combination of Na and one or more additional alkalimetal; B is one or more alkali earth metal; L is selected from Eu, Ce,Tb, Yb, and Pr; L′ is selected from Tl, In, and Na; L″ is selected fromTl and In; and X is one or more halide. In some embodiments, A or A′ isselected from K, Rb, and Cs. In some embodiments, B is selected from Srand Ba. In some embodiments, X is selected from Cl, Br, and I. In someembodiments, L is Eu and the scintillator material comprisesA₂B_((1-z))Eu_(z)X₄ or AB_(2(1-z))Eu_(2z)X₅.

In some embodiments, 0.01≦z≦0.1. In some embodiments, 0.025≦z≦0.05. Insome embodiments, the scintillation material comprisesA₂B_(0.95)Eu_(0.05)X₄ or AB_(2(0.975))Eu_(2(0.025))X₅. In someembodiments, the scintillation material is selected from the groupcomprising K₂BaI₄:Eu 5%; K₂BaBr₄:Eu 5%; Rb₂BaCl₄:Eu 5%; K₂SrBr₄:Eu 5%;Rb₂BaCl₄:Eu 2.5%; RbSr₂Cl₅:Eu 2.5%; KSr₂Br₅:Eu 2.5%; KBa₂I₅:Eu 2.5%;CsSr₂I₅:Eu 2.5%; RbBa₂Br₅:Eu 2.5%; RbSr₂Br₅:Eu 2.5%; KSr₂I₅:Eu 4%; andKSr₂I₅:Eu 2.5%.

In some embodiments, z is 1. In some embodiments, the scintillationmaterial is K₂EuCl₄ or RbEu₂Cl₅.

In some embodiments, the detector is a medical diagnostic device, adevice for oil exploration, or a device for container or baggagescanning. In some embodiments, the presently disclosed subject matterprovides a method of detecting gamma rays, X-rays, cosmic rays, and/orparticles having an energy of 1 keV or greater, the method comprisingusing the radiation detector.

In some embodiments, the presently disclosed subject matter provides amethod of preparing a scintillator material comprising one of Formulas(I), (II), (III), (IV), (V), or (VI) wherein the method comprisesheating a mixture of raw materials above their respective meltingtemperatures. In some embodiments, the method comprises: (a) providing amixture of raw materials, wherein the raw materials are provided in astoichiometric ratio according to one of Formulas (I), (II), (III),(IV), (V), or (VI); (b) sealing said mixture in a sealed container; (c)heating the mixture to about 20° C. above the melting point of the rawmaterial having the highest melting point for a period of time; (d)cooling the mixture to about room temperature; and (e) optionallyrepeating steps (c) and (d). In some embodiments, the scintillatormaterial is prepared in polycrystalline form.

Accordingly, it is an object of the presently disclosed subject matterto provide ternary metal halide scintillator materials and radiationdetectors comprising ternary metal halide scintillator materials;methods of detecting gamma rays, X-rays, cosmic rays and/or particleshaving an energy of 1 keV or greater with the radiation detectors; andmethods of preparing the scintillator materials.

An object of the presently disclosed subject matter having been statedhereinabove, and which is achieved in whole or in part by the presentlydisclosed subject matter, other objects will become evident as thedescription proceeds herein below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the moisture intake curves (at 25° C. and 40%relative humidity) for scintillation materials of the presentlydisclosed subject matter. The materials include CsSr₂I₅: Eu 2.5% (-- ----); K₂SrBr₄: Eu 5% (— - - —); KSr₂Br₅: Eu 2.5% (— - — -); K₂BaI₄: Eu 5%(- - - - - ); KBa₂I₅: Eu 2.5% (- - - -); K₂BaBr₄: Eu 5% (•••••••••) andRbSr₂Cl₅: Eu 2.5% (-------). The moisture intake curves for 5 atomic %cerium activated lanthanum tribromide (LaBr₃:Ce 5%; (— —)) and thalliumactivated sodium iodide (NaI: Tl; (—)) are also shown, for comparison.

FIG. 2A is a graph showing the photoluminescence emission (solid line)and excitation (broken line) spectra of 5 atomic % europium activatedpotassium barium iodide (K₂BaI₄:Eu 5%). There is a broad excitationrange from about 280 nanometers (nm) to about 420 nm and an emissionpeak at 440 nm.

FIG. 2B is a graph showing the photoluminescence emission (broken line)and excitation (solid line) spectra of 5 atomic % europium activatedpotassium barium bromide (K₂BaBr₄:Eu 5%). There is a broad excitationrange from about 280 nanometers (nm) to about 410 nm and an emissionpeak at 434 nm.

FIG. 2C is a graph showing the photoluminescence emission (solid line)and excitation (broken line) spectra of potassium europium chloride(K₂EuCl₄). There is a broad excitation range from about 300 nanometers(nm) to about 427 nm and an emission peak at 474 nm.

FIG. 2D is a graph showing the photoluminescence emission (broken line)and excitation (solid line) spectra of 2.5 atomic % europium activatedrubidium barium chloride (Rb₂BaCl₄:Eu 2.5%). There is a broad excitationrange from about 260 nanometers (nm) to about 406 nm and an emissionpeak at 437 nm.

FIG. 2E is a graph showing the photoluminescence emission (broken line)and excitation (solid line) spectra of 5 atomic % europium activatedpotassium strontium bromide (K₂SrBr₄:Eu 5%). There is a broad excitationrange from about 286 nanometers (nm) to about 410 nm and an emissionpeak at 434 nm.

FIG. 2F is a graph showing the photoluminescence emission (broken line)and excitation (solid line) spectra of 2.5 atomic % europium activatedrubidium strontium chloride (RbSr₂Cl₅:Eu 2.5%). There is a broadexcitation range from about 280 nanometers (nm) to about 415 nm and anemission peak at 426 nm.

FIG. 2G is a graph showing the photoluminescence emission (broken line)and excitation (solid line) spectra of 2.5 atomic % europium activatedpotassium strontium bromide (KSr₂Br₅:Eu 2.5%). There is a broadexcitation range from about 280 nanometers (nm) to about 420 nm and anemission peak at 432 nm.

FIG. 2H is a graph showing the photoluminescence emission (broken line)and excitation (solid line) spectra of 2.5 atomic % europium activatedpotassium barium iodide (KBa₂I₅:Eu 2.5%). There is a broad excitationrange from about 280 nanometers (nm) to about 415 nm and an emissionpeak at 441 nm.

FIG. 2I is a graph showing the photoluminescence emission (broken line)and excitation (solid line) spectra of 2.5 atomic % europium activatedcesium strontium iodide (CsSr₂I₅:Eu 2.5%). There is a broad excitationrange from about 285 nanometers (nm) to about 420 nm and an emissionpeak at 446 nm.

FIG. 2J is a graph showing the photoluminescence emission (solid line)and excitation (broken line) spectra of 2.5 atomic % europium activatedrubidium strontium bromide (RbSr₂Br₅:Eu 2.5%). There is a broadexcitation range from about 270 nanometers (nm) to about 411 nm and anemission peak at 427 nm.

FIG. 2K is a graph showing the photoluminescence emission (solid line)and excitation (broken line) spectra of rubidium europium chloride(RbEu₂Cl₅). There is a broad excitation range from about 270 nanometers(nm) to about 429 nm and an emission peak at 440 nm.

FIG. 2L is a graph showing the photoluminescence emission (solid line)and excitation (broken line) spectra of 2.5 atomic % europium activatedrubidium barium bromide (RbBa₂Br₅:Eu 2.5%). There is a broad excitationrange from about 270 nanometers (nm) to about 401 nm and an emissionpeak at 427 nm.

FIG. 2M is a graph showing the photoluminescence emission (solid line)and excitation (broken line) spectra of 4 atomic % europium activatedpotassium strontium iodide (KSr₂I₅:Eu 4%). There is a broad excitationrange from about 316 nanometers (nm) to about 433 nm and an emissionpeak at 446 nm.

FIG. 3A is a graph showing the x-ray excited luminescence spectra of 5atomic % europium activated potassium barium iodide (K₂BaI₄:Eu 5%). Theemission peak is at 449 nanometers (nm).

FIG. 3B is a graph showing the x-ray excited luminescence spectra of 5atomic % europium activated potassium barium bromide (K₂BaBr₄:Eu 5%).The emission peak is at 430 nanometers (nm).

FIG. 3C is a graph showing the x-ray excited luminescence spectra ofpotassium europium chloride (K₂EuCl₄). The emission peak is at 475nanometers (nm).

FIG. 3D is a graph showing the x-ray excited luminescence spectra of 5atomic % europium activated rubidium barium chloride (Rb₂BaCl₄:Eu 5%).The emission peak is at 436 nanometers (nm).

FIG. 3E is a graph showing the x-ray excited luminescence spectra of 5atomic % europium activated potassium strontium bromide (K₂SrBr₄:Eu 5%).The emission peak is at 445 nanometers (nm).

FIG. 3F is a graph showing the x-ray excited luminescence spectra of 2.5atomic % europium activated rubidium strontium chloride (RbSr₂Cl₅:Eu2.5%). The emission peak is at 426 nanometers (nm).

FIG. 3G is a graph showing the x-ray excited luminescence spectra of 2.5atomic % europium activated potassium strontium bromide (KSr₂Br₅:Eu2.5%). The emission peak is at 427 nanometers (nm).

FIG. 3H is a graph showing the x-ray excited luminescence spectra of 2.5atomic % europium activated potassium barium iodide (KBa₂I₅:Eu 2.5%).

The emission peak is at 442 nanometers (nm).

FIG. 3I is a graph showing the x-ray excited luminescence spectra of 2.5atomic % europium activated cesium strontium iodide (CsSr₂I₅:Eu 2.5%).The emission peak is at 441 nanometers (nm).

FIG. 3J is a graph showing the x-ray excited luminescence spectra of 2.5atomic % europium activated rubidium strontium bromide (RbSr₂Br₅:Eu2.5%). The emission peak is at 430 nanometers (nm).

FIG. 3K is a graph showing the x-ray excited luminescence spectra ofrubidium europium chloride (RbEu₂Cl₅). The emission peak is at 440nanometers (nm).

FIG. 3L is a graph showing the x-ray excited luminescence spectra of 2.5atomic % europium activated rubidium barium bromide (RbBa₂Br₅:Eu 2.5%).The emission peak is at 425 nanometers (nm).

FIG. 3M is a graph showing the x-ray excited luminescence spectra of 2.5atomic % europium activated potassium strontium iodide (KSr₂I₅:Eu 2.5%).The emission peak is at 452 nanometers (nm).

FIG. 4A is a graph showing the light output of 5 atomic % europiumactivated potassium barium iodide (K₂BaI₄:Eu 5%) exposed to gamma-rayenergy. The photopeak is at channel number 806.

FIG. 4B is a graph showing the light output of 5 atomic % europiumactivated potassium barium bromide (K₂BaBr₄:Eu 5%) exposed to gamma-rayenergy. The photopeak is at channel 700.

FIG. 4C is a graph showing the light output of potassium europiumchloride (K₂EuCl₄) exposed to gamma-ray energy. The photopeak is atchannel 367.

FIG. 4D is a graph showing the light output of 5 atomic % europiumactivated rubidium barium chloride (Rb₂BaCl₄:Eu 5%) exposed to gamma-rayenergy. The photopeak is at channel 335.

FIG. 4E is a graph showing the light output of 5 atomic % europiumactivated potassium strontium bromide (K₂SrBr₄:Eu 5%) exposed togamma-ray energy. The photopeak is at channel 400.

FIG. 4F is a graph showing the light output of 2.5 atomic % europiumactivated rubidium strontium chloride (RbSr₂Cl₅:Eu 2.5%) exposed togamma-ray energy. The photopeak is at channel 670.

FIG. 4G is a graph showing the light output of 2.5 atomic % europiumactivated potassium strontium bromide (KSr₂Br₅:Eu 2.5%) exposed togamma-ray energy. The photopeak is at channel 1050.

FIG. 4H is a graph showing the light output of 2.5 atomic % europiumactivated potassium barium iodide (KBa₂I₅:Eu 2.5%) exposed to gamma-rayenergy. The photopeak is at channel 1115.

FIG. 4I is a graph showing the light output of 2.5 atomic % europiumactivated cesium strontium iodide (CsSr₂I₅:Eu 2.5%) exposed to gamma-rayenergy. The photopeak is at channel 993.

FIG. 4J is a graph showing the light output of 2.5 atomic % europiumactivated rubidium strontium bromide (RbSr₂Br₅:Eu 2.5%) exposed togamma-ray energy. The photopeak is at channel 662.

FIG. 4K is a graph showing the light output of rubidium europiumchloride (RbEu₂Cl₅) exposed to gamma-ray energy. The photopeak is atchannel 580.

FIG. 4L is a graph showing the light output of 2.5 atomic % europiumactivated rubidium barium bromide (RbBa₂Br₅:Eu 2.5%) exposed togamma-ray energy. The photopeak is at channel 585.

FIG. 4M is a graph showing the light output of 4 atomic % europiumactivated potassium strontium iodide (KSr₂I₅:Eu 4%) exposed to gamma-rayenergy. The photopeak is at channel 1510.

FIG. 5A is a graph showing the scintillation decay curve for 5 atomic %europium activated potassium barium iodide (K₂BaI₄:Eu 5%).

FIG. 5B is a graph showing the scintillation decay curve for 5 atomic %europium activated potassium barium bromide (K₂BaBr₄:Eu 5%).

FIG. 5C is a graph showing the scintillation decay curve for potassiumeuropium chloride (K₂EuCl₄).

FIG. 5D is a graph showing the scintillation decay curve for 5 atomic %europium activated potassium strontium bromide (K₂SrBr₄:Eu 5%).

FIG. 5E is a graph showing the scintillation decay curve for 5 atomic %europium activated rubidium barium chloride (Rb₂BaCl₄:Eu 5%).

FIG. 5F is a graph showing the scintillation decay curve for 2.5 atomic% europium activated rubidium strontium chloride (RbSr₂Cl₅:Eu 2.5%).

FIG. 5G is a graph showing the scintillation decay curve for 2.5 atomic% europium activated potassium strontium bromide (KSr₂Br₅:Eu 2.5%).

FIG. 5H is a graph showing the scintillation decay curve for 2.5 atomic% europium activated potassium barium iodide (KBa₂I₅:Eu 2.5%).

FIG. 5I is a graph showing the scintillation decay curve for 2.5 atomic% europium activated cesium strontium iodide (CsSr₂I₅:Eu 2.5%).

FIG. 5J is a graph showing the scintillation decay curve for 2.5 atomic% europium activated rubidium strontium bromide (RbSr₂Br₅:Eu 2.5%).

FIG. 5K is a graph showing the scintillation decay curve for rubidiumeuropium chloride (RbEu₂Cl₅).

FIG. 5L is a graph showing the scintillation decay curve for 2.5 atomic% europium activated rubidium barium bromide (RbBa₂Br₅:Eu 2.5%).

FIG. 5M is a graph showing the scintillation decay curve for 4 atomic %europium activated potassium strontium iodide (KSr₂I₅:Eu 4%).

FIG. 6 is a schematic drawing of an apparatus for detecting radiationaccording to the presently disclosed subject matter. Apparatus 10includes photon detector 12 optically coupled to scintillator material14. Apparatus 10 can optionally include electronics 16 for recordingand/or displaying electronic signal from photon detector 12. Thus,optional electronics 16 can be in electronic communication with photondetector 12.

DETAILED DESCRIPTION

The presently disclosed subject matter will now be described more fully.The presently disclosed subject matter can, however, be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein below and in the accompanying Examples.Rather, these embodiments are provided so that this disclosure will bethorough and complete, and will fully convey the scope of theembodiments to those skilled in the art.

All references listed herein, including but not limited to all patents,patent applications and publications thereof, and scientific journalarticles, are incorporated herein by reference in their entireties tothe extent that they supplement, explain, provide a background for, orteach methodology, techniques, and/or compositions employed herein.

I. Definitions

While the following terms are believed to be well understood by one ofordinary skill in the art, the following definitions are set forth tofacilitate explanation of the presently disclosed subject matter.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skill inthe art to which the presently disclosed subject matter belongs.

Following long-standing patent law convention, the terms “a”, “an”, and“the” refer to “one or more” when used in this application, includingthe claims.

The term “and/or” when used in describing two or more items orconditions, refers to situations where all named items or conditions arepresent or applicable, or to situations wherein only one (or less thanall) of the items or conditions is present or applicable.

The use of the term “or” in the claims is used to mean “and/or” unlessexplicitly indicated to refer to alternatives only or the alternativesare mutually exclusive, although the disclosure supports a definitionthat refers to only alternatives and “and/or.” As used herein “another”can mean at least a second or more.

The term “comprising”, which is synonymous with “including,”“containing,” or “characterized by” is inclusive or open-ended and doesnot exclude additional, unrecited elements or method steps. “Comprising”is a term of art used in claim language which means that the namedelements are essential, but other elements can be added and still form aconstruct within the scope of the claim.

As used herein, the phrase “consisting of” excludes any element, step,or ingredient not specified in the claim. When the phrase “consists of”appears in a clause of the body of a claim, rather than immediatelyfollowing the preamble, it limits only the element set forth in thatclause; other elements are not excluded from the claim as a whole.

As used herein, the phrase “consisting essentially of” limits the scopeof a claim to the specified materials or steps, plus those that do notmaterially affect the basic and novel characteristic(s) of the claimedsubject matter.

With respect to the terms “comprising”, “consisting of”, and “consistingessentially of”, where one of these three terms is used herein, thepresently disclosed and claimed subject matter can include the use ofeither of the other two terms.

Unless otherwise indicated, all numbers expressing quantities of time,temperature, light output, atomic percentage (%), and so forth used inthe specification and claims are to be understood as being modified inall instances by the term “about”. Accordingly, unless indicated to thecontrary, the numerical parameters set forth in this specification andattached claims are approximations that can vary depending upon thedesired properties sought to be obtained by the presently disclosedsubject matter.

As used herein, the term “about”, when referring to a value is meant toencompass variations of in one example ±20% or ±10%, in another example±5%, in another example ±1%, and in still another example ±0.1% from thespecified amount, as such variations are appropriate to perform thedisclosed methods.

The term “scintillator” refers to a material that emits light (e.g.,visible light) in response to stimulation by high energy radiation(e.g., X, α, β, or γ radiation).

In some embodiments, the compositional formula expression of ascintillator material can contain a colon “:”, wherein the compositionof the main scintillation material is indicated on the left side of thecolon, and the activator or dopant ion is indicated on the right side ofthe colon. The atomic percentage of the dopant or activator ion can alsobe indicated to the right side of the colon. For the presently disclosedternary metal scintillators that comprise an alkali metal and an alkaliearth metal, the atomic percentage of a divalent dopant ion (e.g.,divalent europium ion) can be expressed in atomic percentage relative tothe total amount of dopant and alkali earth metal. Thus, the dopant ioncan be a divalent ion that substitutes for a percentage of the divalentalkali earth metal ion in the base (i.e., main or un-doped) ternarymetal halide composition. For example, K₂BaBr₄:Eu 5% represents aK₂BaBr₄ scintillator material activated by europium, wherein 5 atomic %of the barium is replaced by europium. In some embodiments, the dopantis a monovalent ion that substitutes for a percentage of the alkalimetal ion in the base ternary metal halide composition. Thus, the atomic% of a monovalent dopant can be expressed as the atomic % relative tothe total amount of dopant and alkali metal.

The term “high energy radiation” can refer to electromagnetic radiationhaving energy higher than that of ultraviolet radiation, including, butnot limited to X radiation (i.e., X-ray radiation), alpha (α) particles,gamma (γ) radiation, and beta (β) radiation. In some embodiments, thehigh energy radiation refers to gamma rays, cosmic rays, X-rays, and/orparticles having an energy of 1 keV or greater. Scintillator materialsas described herein can be used as components of radiation detectors inapparatuses such as counters, image intensifiers, and computedtomography (CT) scanners.

“Optical coupling” as used herein refers to a physical coupling betweena scintillator and a photosensor, e.g., via the presence of opticalgrease or another optical coupling compound (or index matching compound)that bridges the gap between the scintillator and the photosensor. Inaddition to optical grease, optical coupling compounds can include, forexample, liquids, oils and gels.

“Light output” can refer to the number of light photons produced perunit energy deposited, e.g., by a gamma ray being detected, typicallythe number of light photons/MeV.

As used herein, chemical ions are typically represented simply by theirchemical element symbols alone (e.g., Eu for europium ion(s) (e.g.,Eu²⁺) or Na for sodium ion(s) (e.g., Na⁺)). Similarly, the terms “alkalimetal” and “alkali earth metal” are used herein to refer to an alkalimetal ion or ions and an alkali earth metal ion or ions, respectively.

II. General Considerations

In some embodiments, the presently disclosed subject matter provides ascintillator material that comprises a ternary metal halide doped oractivated with europium (Eu) and/or one or more other dopants (e.g.,cerium (Ce), praseodymium (Pr), terbium (Tb), ytterbium (Yb), thallium(Tl), indium (In), sodium (Na), and other dopants that can luminesce inresponse to the absorption of energy). For instance, the base ternarymetal halide being activated or doped can have a formula A₂BX₄ or AB₂X₅,wherein A is an alkali metal or metals, B is an alkali earth metal ormetals; and X is one or more halide. In some embodiments, the baseternary metal halide being activated or doped can have the formulaA′₂BX₄ or A′B₂X₅, wherein A′ is an alkali metal or metals other than Na;B is one or more alkali earth metal; and X is one or more halide. Insome embodiments, the base ternary metal halide being activated or dopedcan have the formula A″₂BX₄ or A″B₂X₅, wherein A″ is Na or a combinationof Na and one or more additional alkali metal; B is one or more alkaliearth metal; and X is one or more halide. The europium dopant, otherdopant, or dopant mixture can replace all or a portion of the alkaliearth metal (e.g., if the dopant ion is divalent or includes divalentions) and/or all or a portion of the alkali metal (if the dopant ion isor includes monovalent ions).

In some embodiments, the dopant or dopants replaces up to about 50atomic % of the alkali earth metal(s) or alkali metal(s) (e.g., up toabout 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2, or about 1 atomic% of the alkali earth metal(s) or alkali metal(s)). In some embodiments,the dopant or dopants replaces up to about 20 atomic % of the alkaliearth metal(s) or alkali metal(s) or between about 2.5 atomic % andabout 10 atomic % of the alkali earth metal(s) or alkali metal(s).

In some embodiments, the presently disclosed subject matter provides aternary metal halide scintillator material of one of the Formulas (I),(II), (IIIa), or (IVa):

A₂B_((1-y))L_(y)X₄  (I);

AB_(2(1-y))L_(2y)X₅  (II);

A_(2(1-y))L′_(2y)BX₄  (IIIa); or

A_((1-y))L′_(y)B₂X₅  (IVa);

wherein: A is one or more alkali metal, such as lithium (Li), sodium(Na), potassium (K), rubidium (Rb), cesium (Cs), or a combinationthereof; B is one or more alkali earth metal, such as beryllium (Be),magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), or acombination thereof; L is a divalent dopant or mixture of divalentdopants (e.g., selected from Eu, Ce, Tb, Yb, and Pr); L′ is a monovalentdopant or mixture of monovalent dopants (e.g., selected from Tl, In, andNa); and X is one or more halide, such as fluoride (F), chloride (Cl),bromide (Br), iodide (I), or a combination thereof; and 0.0001≦y≦0.5,subject to the proviso that, in materials of Formula (IIIa) or Formula(IVa), when A is Na or a combination of Na and one or more additionalalkali metal, L′ is a monovalent dopant or mixture of monovalent dopantsother than Na (e.g., L′ is selected from Tl and In). Thus, in someembodiments, the scintillator materials can comprise europium- and/orother dopant-containing metal tetra- and pentahalides, wherein the metaltetra- and pentahalides can comprise alkali metal and alkali earth metalions. In some embodiments, the scintillator material can comprise amixture of two or more materials of Formulas (I), (II), (IIIa), and/or(IVa).

In some embodiments, the presently disclosed subject matter provides aternary metal halide scintillator material of one of the Formulas (I),(II), (III), (IV), (V) or (VI):

A₂B_((1-y))L_(y)X₄  (I);

AB_(2(1-y))L_(2y)X₅  (II);

A′_(2(1-y))L_(2y)BX₄  (III);

A′_((1-y))L′_(y)B₂X₅  (IV);

A″_(2(1-y))L″_(2y)BX₄  (V); or

A″_((1-y))L″_(y)B₂X₅  (VI);

wherein: A is one or more alkali metal, such as Li, Na, K, Rb, Cs, or acombination thereof; A′ is one or more alkali metal other than Na; A″ isNa or a combination of Na and one or more additional alkali metal (e.g.,Li, K, Rb, or Cs); B is one or more alkali earth metal, such as Be, Mg,Ca, Sr, Ba, or a combination thereof; L is a divalent dopant or mixtureof divalent dopants (e.g., selected from Eu, Ce, Tb, Yb and Pr); L′ is amonovalent dopant or mixture of monovalent dopants (e.g., selected fromTl, In, and Na); L″ is a monovalent dopant other than Na (e.g., isselected from Tl and In); and X is one or more halide, such as F, Cl,Br, I, or a combination thereof; and wherein 0.0001≦y≦0.5. In someembodiments, the scintillator material can comprise a mixture of two ormore materials of Formulas (I), (II), (III), (IV), (V), and/or (VI).

Alkali metal A can be any suitable alkali metal or combination of alkalimetals. In some embodiments, A is selected from the group comprising Li,Na, K, Rb, Cs, and combinations thereof. In some embodiments, A′ isselected from the group comprising Li, K, Rb, and Cs. In someembodiments, A or A′ is selected from the group comprising K, Rb, andCs. In some embodiments, A″ is Na or a combination of Na and one or moreof Li, K, Rb and Cs.

Alkali earth metal B can be any suitable alkali earth metal orcombination of alkali earth metals. In some embodiments, B is selectedfrom the group comprising Be, Mg, Ca, Sr, Ba, and combinations thereof.In some embodiments, B is selected from Sr and Ba.

Halide X can be any suitable halide or combination of halides, e.g., I,F, Br, and Cl. In some embodiments, X is selected from Cl, Br, and I.

In some embodiments, L is Eu, Ce Tb, Yb, or Pr. In some embodiments, Lis Eu, Ce, or Pr. In some embodiments, L is Eu (which can be present asEu²⁺). In some embodiments, L (e.g. Eu) replaces about 20 atomic % orless of the alkali earth metal or metals. In some embodiments L (e.g.,Eu) replaces between about 1 atomic % and about 10 atomic % of thealkali earth metal or metals. In some embodiments, 0.01≦y≦0.1 (e.g., yis about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or about0.10). In some embodiments, 0.025≦y≦0.05. In some embodiments, L (e.g.,Eu) replaces about 2.5, 4, or about 5 atomic % of the alkali earthmetal. In some embodiments, the scintillator material has one of theformulas: A₂B_(0.95)Eu_(0.05)X₄ or AB_(2(0.975))Eu_(2(0.025))X₅.

In some embodiments, L′ is Tl, In, or Na, and L′ replaces about 20atomic % or less of the alkali metal or metals A′. In some embodiments,L′ replaces between about 1 atomic % and about 10 atomic % of the alkalimetal or metals A′ (e.g., y is about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06,0.07, 0.08, 0.09 or about 0.10). In some embodiments, 0.025≦y≦0.05.

In some embodiments, L″ is Tl or In and L″ replaces about 20 atomic % orless of A″. In some embodiments, L″ replaces between about 1 atomic %and about 10 atomic % of the alkali metal or metals A″ (e.g., y is about0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or about 0.10). Insome embodiments, 0.025≦y≦0.05.

Exemplary scintillation materials of the presently disclosed subjectmatter can include, but are not limited to, K₂BaI₄:Eu 5%; K₂BaBr₄:Eu 5%;Rb₂BaCl₄:Eu 5%; K₂SrBr₄:Eu 5%; Rb₂BaCl₄:Eu 2.5%; RbSr₂Cl₅:Eu 2.5%;KSr₂Br₅:Eu 2.5%; KBa₂I₅:Eu 2.5%; CsSr₂I₅:Eu 2.5%; RbBa₂Br₅:Eu 2.5%;RbSr₂Br₅:Eu 2.5%; KSr₂I₅:Eu 4%; and KSr₂I₅:Eu 2.5%.

In some embodiments, the activator or dopant can replace up to about 100atomic % of the alkali metal or metals or of the alkali earth metal ormetals. Thus, in some embodiments, the scintillator material cancomprise one of Formulas (I′), (II′), (IIIa′), or (IVa′);

A₂B_((1-z))L_(z)X₄  (I′);

AB_(2(1-z))L_(2z)X₅  (II′);

A_(2(1-z))L′_(2z)BX₄  (IIIa′); or

A_((1-z))L′_(z)B₂X₅  (IVa′);

wherein: 0.0001≦z≦1.0, and A is one or more alkali metal (e.g., Li, Na,K, Rb, or Cs); B is one or more alkali earth metal (e.g., Be, Mg, Ca,Sr, or Ba), L is a divalent dopant or mixture of divalent dopants (e.g.,Eu, Ce, Tb, Yb, or Pr); L′ is a monovalent dopant or mixture ofmonovalent dopants (e.g., Tl, In, or Na); and X is one or more halide,subject to the proviso that, in materials of Formula (IIIa′) or (IVa′),when A is Na or a combination of Na and one or more additional alkalimetal, L′ is other than Na (e.g., L′ is Tl or In). In some embodiments,the scintillator material can comprise a mixture of two or morematerials of Formulas (I′), (II′), and/or (IVa′).

In some embodiments, the scintillator material can comprise one ofFormulas (I′), (II′), (III′), (IV′), (V′) or (VI′):

A₂B_((1-z))L_(z)X₄  (I′);

AB_(2(1-z))L_(2z)X₅  (II′);

A′_(2(1-z))L′_(2z)BX₄  (III′);

A′_((1-z))L′_(z)B₂X₅  (IV);

A″_(2(1-z))L″_(2z)BX₄  (V′); or

A″_((1-z))L″_(z)B₂X₅  (VI′);

wherein 0.0001≦z≦1.0 and wherein A, A′, A″, B, L, L′, and L″ are asdefined for Formulas (I), (II), (III), (IV), (V), and (VI). In someembodiments, the scintillator material can comprise a mixture of two ormore materials of Formulas (I′), (II′), (III′), (IV′), (V′), and/or(VI′).

In some embodiments, 0.01≦z≦1.1. In some embodiments, 0.025≦z≦0.05. Insome embodiments, the scintillation material of Formulas (I′) or (II′)can comprise A₂B_(0.95)Eu_(0.05)X₄ or AB_(2(0.975))Eu_(2(0.025))X₅. Insome embodiments, the scintillator material of Formulas (I′) or (II′)can be selected from the group comprising, but not limited to: K₂BaI₄:Eu5%; K₂BaBr₄:Eu 5%; Rb₂BaCl₄:Eu 5%; K₂SrBr₄:Eu 5%; Rb₂BaCl₄:Eu 2.5%;RbSr₂Cl₅:Eu 2.5%; KSr₂Br₅:Eu 2.5%; KBa₂I₅:Eu 2.5%; CsSr₂I₅:Eu 2.5%;RbBa₂Br₅:Eu 2.5%; RbSr₂Br₅:Eu 2.5%; KSr₂I₅:Eu 4%; and KSr₂I₅:Eu 2.5%.

In some embodiments, 0.5≦z≦1.0 (i.e., z is greater than 0.5 and lessthan or equal to 1). Thus, in some embodiments, the activator or dopantreplaces between about 50.01 atomic % and about 100 atomic % of thealkali metal(s) or alkali earth metal(s).

In some embodiments, z is 1; the alkali earth metal is not present; andthe scintillation material comprises A₂LX₄ or AL₂X₅. In someembodiments, L is Eu and the scintillation material has one of theformulas: A₂EuX₄ or AEu₂X₅, wherein A is one or more alkali metal and Xis one or more halide. In some embodiments, A is selected from the groupcomprising K, Rb, and Cs. In some embodiments, X is selected from Cl,Br, and I. In some embodiments, the scintillation material is K₂EuCl₄ orRbEu₂Cl₅.

In some embodiments, z is 1; the alkali metal is not present; and thescintillation material comprises L′₂BX₄ or L′B₂X₅, e.g., wherein L′ isTl, In, or Na; B is one or more alkali earth metal (e.g., Be, Mg, Ca,Sr, or Ba); and X is one or more halide (e.g., F, Cl, Br, or I). In someembodiments, the scintillation material comprises or L″₂BX₄ or L″B₂X₅wherein L″ is Tl or In; B is one or more alkali earth metal; and X isone or more halide. In some embodiments, B is Sr or Ba. In someembodiments, X is Cl, Br, or I.

The scintillation material can be a single crystal, a polycrystallinematerial, and/or a ceramic. By “single crystal” is meant a materialmanufactured by a liquid phase method having few or no grain boundariesand wherein each adjoining crystal grain generally has the sameorientation. In some embodiments, the material can be polycrystallineand/or ceramic and contain crystals of varying size and/or orientation.

The presently disclosed scintillation materials can have high lightoutput, useful emission wavelength, low melting points, congruentmelting, and practical crystal growth. In some embodiments, thescintillation material has a relatively low tendency to absorb water,e.g., compared to other known metal halide scintillation compounds. Insome embodiments, the material is less hygroscopic than LaBr₃:Ce (e.g.,at 25° C. and 40% relative humidity) In some embodiments, the materialis less hygroscopic than NaI:Tl (e.g., at 25° C. and 40% relativehumidity). In some embodiments, the material has an about 2% or less(e.g., about 2.0, 1.5, 1.0, 0.5% or less) weight change under desiredconditions, such as at 25° C. and 40% relative humidity or at 25° C. and70% relative humidity, over a period of about one hour or more.

IV. Radiation Detectors, Related Devices and Methods

In some embodiments, the presently disclosed subject matter provides aradiation detector comprising a scintillator material as describedhereinabove or a mixture of such materials. The radiation detector cancomprise a scintillator (which absorbs radiation and emits light) and aphotodetector (which detects said emitted light). The photodetector canbe any suitable detector or detectors and can be or not be opticallycoupled to the scintillator material for producing an electrical signalin response to emission of light from the scintillator material. Thus,the photodetector can be configured to convert photons to an electricalsignal. For example, a signal amplifier can be provided to convert anoutput signal from a photodiode into a voltage signal. The signalamplifier can also be designed to amplify the voltage signal.Electronics associated with the photodetector can be used to shape anddigitize the electronic signal.

Referring now to FIG. 6, in some embodiments, the presently disclosedsubject matter provides an apparatus 10 for detecting radiation whereinthe apparatus comprises a photon detector 12 and a scintillator material14 (e.g., a europium-containing ternary metal halide). Scintillatormaterial 14 can convert radiation to light that can be collected by acharge-coupled device (CCD) or a photomultiplier tube (PMT) or otherphoton detector 12 efficiently and at a fast rate.

Referring again to FIG. 6, photon detector 12 can be any suitabledetector or detectors and can be optically coupled (e.g., via opticalgrease or another optical coupling compound, such as an optical couplingoil or liquid) to the scintillator (e.g., the europium containingternary metal halide) for producing an electrical signal in response toemission of light from the scintillator. Thus, photon detector 12 can beconfigured to convert photons to an electrical signal. Electronicsassociated with photon detector 12 can be used to shape and digitize theelectronic signal. Suitable photon detectors 12 include, but are notlimited to, photomultiplier tubes, photodiodes, CCD sensors, and imageintensifiers. Apparatus 10 can also include electronics 16 for recordingand/or displaying the electronic signal.

In some embodiments, the radiation detector is configured for use aspart of a medical or veterinary diagnostic device, a device for oil orother geological exploration (e.g., oil well logging probes), or as adevice for security and/or military-related purposes (e.g., as a devicefor container, vehicle, or baggage scanning or for scanning humans orother animals). In some embodiments, the medical or veterinarydiagnostic device is selected from, but not limited to, a positronemission tomography (PET) device, an X-ray computed tomography (CT)device, a single photon emission computed tomography (SPECT) device, ora planar nuclear medical imaging device. For example, the radiationdetector can be configured to move (e.g., via mechanical and/orelectronic controls) over and/or around a sample, such as a human oranimal subject, such that it can detect radiation emitted from anydesired site or sites on the sample. In some embodiments, the detectorcan be set or mounted on a rotating body to rotate the detector around asample.

In some embodiments, the device can also include a radiation source. Forinstance, an X-ray CT device of the presently disclosed subject mattercan include an X-ray source for radiating X-rays and a detector fordetecting said X-rays. In some embodiments, the device can comprise aplurality of radiation detectors. The plurality of radiation detectorscan be arranged, for example, in a cylindrical or other desired shape,for detecting radiation emitted from various positions on the surface ofa sample.

In some embodiments, the presently disclosed subject matter provides amethod for detecting radiation (or the absence of radiation) using aradiation detector comprising a europium- or other dopant-containingternary metal halide scintillator as described hereinabove. Thus, insome embodiments, the presently disclosed subject matter provides amethod of detecting gamma rays, X-rays, cosmic rays and particles havingan energy of 1 keV or greater, wherein the method comprises using aradiation detector comprising a material of one of Formulas (I), (II),(IIIa), (III), (IVa) (IV), (V), (VI), (I′), (II′), (IIIa′), (III′),(IVa′), (IV′), (V′), or (VI′) or a mixture of such materials.

In some embodiments, A or A′ is selected from the group comprising K,Rb, and Cs. In some embodiments, B is selected from the group comprisingSr and Ba. In some embodiments, L is Eu. In some embodiments, X isselected from the group comprising Cl, Br, and I.

In some embodiments, the scintillator material comprises a material ofFormula (I) or (II) and is doped with Eu and/or one or more otherdivalent dopants to replace between about 0.01 atomic % and about 50atomic % of the alkali earth metal (i.e., wherein 0.0001≦y≦0.5). In someembodiments, the material comprises a material of Formula (III) or (IV)and is doped with Tl, In, and/or Na to replace between about 0.01 atomic% and about 50 atomic % of the alkali metal(s) A′ (i.e., wherein0.0001≦y≦0.5). In some embodiments, the material comprises a material ofFormula (V) or (VI) and is doped with Tl or In to replace between about0.01 atomic % and about 50 atomic % of the alkali metal(s) A″. In someembodiments, for any of Formulas (I), (II), (IIIa), (III), (IVa), (IV),(V), or (VI), 0.01≦y≦0.1. In some embodiments, 0.025≦y≦0.05.

In some embodiments, the scintillator material comprisesA₂B_(0.95)Eu_(0.05)X₄ or AB_(2(0.975))Eu_(2(0.025))X₅. In someembodiments, the scintillator material is selected from the groupcomprising K₂BaI₄:Eu 5%; K₂BaBr₄:Eu 5%; Rb₂BaCl₄:Eu 5%; K₂SrBr₄:Eu 5%;Rb₂BaCl₄:Eu 2.5%; RbSr₂Cl₅:Eu 2.5%; KSr₂Br₅:Eu 2.5%; KBa₂I₅:Eu 2.5%;CsSr₂I₅:Eu 2.5%; RbBa₂Br₅:Eu 2.5%; RbSr₂Br₅:Eu 2.5%; KSr₂I₅:Eu 4%; andKSr₂I₅:Eu 2.5%.

In some embodiments, the scintillator material comprises a material ofone of Formulas (I′), (II′), (III′), (IV′), (V′), or (VI′). In someembodiments, 0.0001≦z≦0.5; 0.01≦z≦0.1; or 0.025≦z≦0.05. Thus, in someembodiments, the material of one of Formulas (I′), (II′) (III′), (IV′),(V′), or (VI′) can also be a material of one of Formulas (I), (II),(III) (IV), (V), or (VI), such as, but not limited to, K₂BaI₄:Eu 5%;K₂BaBr₄:Eu 5%; Rb₂BaCl₄:Eu 5%; K₂SrBr₄:Eu 5%; Rb₂BaCl₄:Eu 2.5%;RbSr₂Cl₅:Eu 2.5%; KSr₂Br₅:Eu 2.5%; KBa₂I₅:Eu 2.5%; CsSr₂I₅:Eu 2.5%;RbBa₂Br₅:Eu 2.5%; RbSr₂Br₅:Eu 2.5%; KSr₂I₅:Eu 4%; and KSr₂I₅:Eu 2.5%.

In some embodiments, 0.5<z≦1.0. In some embodiments, z is 1 or about 1and about 100% of the alkali metal or alkali earth metal is replaced byan activator or dopant.

In some embodiments, the alkali earth metal is not present and thematerial comprises one or more alkali metal, Eu, and one or more halide.Thus, in some embodiments, the material comprises:

A₂EuX₄ or AEu₂X₅,

wherein A is one or more alkali metal; and X is one or more halide. Insome embodiments, the material is selected from the group comprisingK₂EuCl₄ and RbEu₂Cl₅.

In some embodiments, the method can comprise providing a radiationdetector comprising a photodetector and a scintillator material of thepresently disclosed subject matter; positioning the detector, whereinthe positioning comprises placing the detector in a location wherein thescintillator material is in the path of a beam of radiation (or thesuspected path of a beam of radiation); and detecting light (ordetecting the absence of light) emitted by the scintillator materialwith the photodetector. Detecting the light emitted by the scintillatormaterial can comprise converting photons to an electrical signal.Detecting can also comprise processing the electrical signal to shape,digitize, or amplify the signal. The method can further comprisedisplaying the electrical signal or processed electrical signal.

In some embodiments, the presently disclosed subject matter provides adevice comprising a photodetector and a scintillator material comprisinga ternary metal tetra- or pentahalide comprising europium and/or one ormore other dopants, such as a material of one of Formulas (I), (II),(IIIa), (III), (IVa), (IV), (V), (VI), (I′), (II′), (IIIa′), (III′),(IVa′), (IV), (V′), and (VI′) or a mixture of such materials. In someembodiments, the device comprising the photodetector and thescintillator material is adapted for use in medical imaging, geologicalexploration, or homeland security. In some embodiments, the presentlydisclosed subject matter provides a method of detecting high energyphotons and particles, wherein the method comprises using the devicecomprising the photodetector and the scintillator material comprising amaterial of one of Formulas (I), (II), (IIIa), (III), (IVa), (IV), (V),(VI), (I′), (II′), (IIIa′), (III′), (IVa′), (IV′), (V′), and (VI′) or amixture of such materials.

In some embodiments, A or A′ is selected from the group comprising K,Rb, and Cs. In some embodiments, B is selected from the group comprisingSr and Ba. In some embodiments, L is Eu. In some embodiments, X isselected from the group comprising Cl, Br, and I.

In some embodiments, the scintillator material is a ternary metal halidedoped with Eu and/or one or more other divalent dopants (e.g., Ce, Tb,Yb, and/or Pr) to replace between about 0.01 atomic % and about 50atomic % of the alkali earth metal(s) (i.e., wherein 0.0001≦y≦0.5 or0.0001≦z≦0.5). In some embodiments, the material comprises a ternarymetal halide doped with Tl, In, and/or Na to replace between about 0.01atomic % and about 50 atomic % of the alkali metal(s) A′ (i.e., wherein0.0001≦y≦0.5 or 0.0001≦z≦0.5). In some embodiments, the materialcomprises a ternary metal halide doped with Tl and/or In to replacebetween about 0.01 atomic % and about 50 atomic % of the alkali metal(s)A″ (i.e., wherein 0.0001≦y≦0.5 or 0.0001≦z≦0.5). In some embodiments,for any of Formulas (I), (II), (IIIa), (III), (IVa), (IV), (V), (VI),(I′), (II′), (IIIa′), (III′), (IVa′), (IV′), (V′), and/or (VI′),0.01≦y≦0.1 or 0.01≦z≦0.1. In some embodiments, 0.025≦y≦0.05 or0.025≦z≦0.05.

In some embodiments, the material comprises A₂B_(0.95)Eu_(0.05)X₄ orAB_(2(0.975))Eu_(2(0.025))X₅. In some embodiments, the material isselected from the group comprising K₂BaI₄:Eu 5%; K₂BaBr₄:Eu 5%;Rb₂BaCl₄:Eu 5%; K₂SrBr₄:Eu 5%; Rb₂BaCl₄:Eu 2.5%; RbSr₂Cl₅:Eu 2.5%;KSr₂Br₅:Eu 2.5%; KBa₂I₅:Eu 2.5%; CsSr₂I₅:Eu 2.5%; RbBa₂Br₅:Eu 2.5%;RbSr₂Br₅:Eu 2.5%; KSr₂I₅:Eu 4%; and KSr₂I₅:Eu 2.5%.

In some embodiments, the scintillator material comprises a material ofone of Formulas (I′), (II′), (IIIa′), (III′), (IVa′), (IV′), (V′), and(VI′) and 0.5<z≦1.0. In some embodiments, z is 1 or about 1 and about100% of the alkali metal or alkali earth metal is replaced by anactivator or dopant.

In some embodiments, the alkali earth metal is not present and thematerial comprises one or more alkali metal, Eu, and one or more halide.Thus, in some embodiments, the material comprises:

A₂EuX₄ or AEu₂X₅,

wherein A is one or more alkali metal; and X is one or more halide. Insome embodiments, the material is selected from the group comprisingK₂EuCl₄ and RbEu₂Cl₅.

V. Methods of Preparation

The presently disclosed scintillation materials can be prepared via anysuitable method. Typically, the appropriate reactants (e.g., metalhalides, such as, but not limited to CsBr, NaBr, CsI, NaI, SrI₂, BaI₂,EuBr₂, and the like) are melted at a temperature sufficient to form acongruent, molten composition. The melting temperature will depend onthe identity of the reactants themselves (e.g., on the melting points ofthe individual reactants), but is usually in the range of from about300° C. to about 1350° C. Exemplary techniques for preparing thematerials include, but are not limited to, the Bridgman orBridgman-Stockbarger method, the Czochralski method, the zone-meltingmethod (or “floating zone” method), the vertical gradient freeze (VGF)method, and temperature gradient methods.

For instance, in some embodiments, high purity reactants can be mixedand melted to synthesize a compound of the desired composition. A singlecrystal or polycrystalline material can be grown from the synthesizedcompound by the Bridgman method, in which a sealed ampoule containingthe synthesized compound is transported from a hot zone to a cold zonethrough a controlled temperature gradient at a controlled speed. In someembodiments, high purity reactants can be mixed in stoichiometric ratiosdepending upon the desired composition of the scintillator material andloaded into an ampoule, which is then sealed. After sealing, the ampouleis heated and then cooled at a controlled speed.

In some embodiments, the presently disclosed subject matter provides amethod of preparing a scintillation material comprising an europium-and/or other dopant-containing ternary metal tetra- or pentahalide. Insome embodiments, the method comprises heating a mixture of rawmaterials (e.g., a mixture of metal halides in a stoichiometric ratiodepending upon the formula of the desired scintillation material) abovetheir respective melting temperatures (i.e., above the meltingtemperature of the raw material with the highest melting temperature).In some embodiments, the raw materials are dried prior to, during, orafter mixing. In some embodiments, the raw materials are mixed under lowhumidity and/or low oxygen conditions. In some embodiments, the rawmaterials are mixed in a dry box and/or under conditions of less thanabout 0.1 parts-per-million (ppm) moisture and/or oxygen (e.g., lessthan about 0.1 ppm, 0.09 ppm, 0.08 ppm, 0.07 ppm, 0.06 ppm, 0.05 ppm,0.04 ppm, 0.03 ppm, 0.02 ppm, or less than 0.01 ppm moisture and/oroxygen).

The mixture of raw materials can be sealed in a container (e.g., aquartz ampoule) that can withstand the subsequent heating of the mixtureand which is chemically inert to the mixture of raw materials. Themixture can be heated at a predetermined rate to a temperature above themelting temperature of the individual raw materials. In someembodiments, the mixture can be heated to a temperature that is betweenabout 10° C. and about 40° C. (e.g., about 10, 12, 14, 16, 18, 20, 22,24, 26, 28, 30, 32, 34, 36, 38, or about 40° C.) above the meltingtemperature of the raw material with the highest melting temperature. Insome embodiments, the mixture is heated to about 20° C. above themelting temperature of the raw material with the highest meltingtemperature. This temperature can be maintained for a period of time,such as between about 2 and about 12 hours (e.g., about 2, 3, 4, 5, 6,7, 8, 9, 10, 11, or about 12 hours). Then the mixture can be cooled at apredetermined rate until the mixture reaches about room temperature(e.g., between about 20° C. and about 25° C.). If desired, the sealedcontainer can be rotated or inverted. Then the heating and cooling canbe repeated, e.g., to provide further mixing of all of the components inthe mixture. The rotating or inverting and heating/cooling steps can berepeated one or more additional times, as desired.

Accordingly, in some embodiments, the method comprises:

(a) providing a mixture of raw materials, wherein the raw materials areprovided in a stoichiometric ratio according to one of Formulas (I),(II), (IIIa), (III), (IVa), (IV), (V), (VI), (I′), (II′), (IIIa′),(III′), (IVa′), (IV′), (V′), and (VI′);

(b) sealing said mixture in a sealed container;

(c) heating the mixture to about 20° C. above the melting point of theraw material having the highest melting point for a period of time;

(d) cooling the mixture to about room temperature; and

(e) optionally repeating steps (c) and (d).

In some embodiments, steps (c) and (d) are repeated one or more times.

In some embodiments, the scintillation material comprises one ofFormulas (I), (II), (III), (IV) (V), or (VI). In some embodiments, A orA′ is selected from the group comprising K, Rb, and Cs. In someembodiments, B is selected from the group comprising Sr and Ba. In someembodiments, L is Eu. In some embodiments, X is selected from the groupcomprising Cl, Br, and I.

In some embodiments, the material comprises at least one alkali earthmetal B and is doped with Eu and/or one or more other divalent dopants(e.g., Ce, Tb, Yb, and/or Pr). In some embodiments, the material is aone of Formulas (I) or (II). In some embodiments 0.01≦y≦0.1. In someembodiments, 0.025≦y≦0.05.

In some embodiments, the scintillation material comprisesA₂B_(0.95)Eu_(0.05)X₄ or AB_(2(0.975))Eu_(2(0.025))X₅. In someembodiments, the scintillation material is selected from the groupcomprising K₂BaI₄:Eu 5%; K₂BaBr₄:Eu 5%; Rb₂BaCl₄:Eu 5%; K₂SrBr₄:Eu 5%;Rb₂BaCl₄:Eu 2.5%; RbSr₂Cl₅:Eu 2.5%; KSr₂Br₅:Eu 2.5%; KBa₂I₅:Eu 2.5%;CsSr₂I₅:Eu 2.5%; RbBa₂Br₅:Eu 2.5%; RbSr₂Br₅:Eu 2.5%; KSr₂I₅:Eu 4%; andKSr₂I₅:Eu 2.5%.

In some embodiments, the alkali earth metal is not present (i.e., z is 1in one of Formulas (I′) or (II′)) and the scintillation materialcomprises one or more alkali metal, Eu, and one or more halide. Thus, insome embodiments, the scintillation material can comprise:

A₂EuX₄ or AEu₂X₅,

wherein A is one or more alkali metal; and X is one or more halide. Insome embodiments, the scintillation material can be selected from thegroup comprising K₂EuCl₄ and RbEu₂Cl₅.

The scintillation materials can be provided as single crystals, as apolycrystalline material, and/or as a ceramic material. In someembodiments, the material is provided as a polycrystalline material. Thepolycrystalline material can have analogous physical, optical andscintillation properties as a single crystal otherwise having the samechemical composition.

EXAMPLES

The following Examples have been included to provide guidance to one ofordinary skill in the art for practicing representative embodiments ofthe presently disclosed subject matter. In light of the presentdisclosure and the general level of skill in the art, those of skill canappreciate that the following Examples are intended to be exemplary onlyand that numerous changes, modifications, and alterations can beemployed without departing from the scope of the presently disclosedsubject matter.

Example 1 Preparation of Scintillator Materials

Anhydrous high purity raw materials (e.g., CsBr, NaBr, CsI, NaI, SrI₂,BaI₂, EuBr₂, and the like) from Sigma-Aldrich (St. Louis, Mo., UnitedStates of America) were mixed and loaded into 8 millimeter (mm) diameterquartz ampoules, inside a dry box containing less than 0.01 ppm moistureand oxygen, and in stoichiometric ratios according to the chemicalformulas of the respective compounds. The mixed raw materials were driedin the ampoules under 10-6 torr vacuum at 200° C. for 4 hours. As soonas the loaded ampoules reached room temperature, they were sealed with ahydrogen torch. A single zone clamshell furnace was used tomelt-synthesize 4 gram (g) samples of the compounds:A₂B_(0.95)Eu_(0.05)X₄ (A=K or Rb; B=Sr or Ba; and X=Cl, Br, or I) andAB_(2(0.975))Eu_(2(0.025))X₅ (A=K, Rb, or Cs; B=Sr or Ba; and X=Cl, Br,or I). The temperature was slowly raised to about 20° C. above themelting points of all the components. This temperature was held for 7hours and slowly brought down to room temperature (over a period ofabout 7 hours). The ampoule was inverted and the procedure was repeatedto encourage complete mixing of all constituents. The result was apolycrystalline sample with analogous physical, optical andscintillation properties of a grown single crystal.

The phase diagrams of KBr—SrBr₂, KBr—BaBr₂, and KCl—EuCl₄ have beenpreviously reported. See Kellner (1917); Riccardi et al. (1970); andKorshunov et al. (1966). The phase diagrams show the formation ofcongruent melting compounds of the formula K₂BX₄ wherein B is Sr, Ba, orEu and X is Br or Cl at 600° C., 632° C., and 605° C., respectively. SeeKellner (1917); Riccardi et al. (1970); and Korshunov et al. (1966).K₂EuCl₄ has a density of 3.2 g/cm³ and tetrahedral crystal structure.See Fink and Seifert (1980). Table 1, below, displays some of thephysical properties of the base ternary metal pentahalide compounds(i.e., the AB₂X₅ compounds without europium doping) of the presentlydisclosed subject matter. Although some of the non-europium dopedcompounds were previously known, they were not previously known asscintillators.

TABLE 1 Physical Properties of AB₂X₅ Compounds. Crystal Structure atMelting Point room Density Compound (° C.) temperature (g/cm³)Hygroscopcity RbSr₂Cl₅ 634^(a) orthorhombic^(e) 3.20^(e) slightlyKSr₂Br₅ 572^(b) monoclinic^(e) 3.98^(e) slightly KBa₂I₅ NImonoclinic^(e) 4.52^(e) slightly CsSr₂I₅ NI monoclinic^(e) 4.64^(e) veryRbEu₂Cl₅ 663^(c) monoclinic^(c) 4.20^(c) slightly RbBa₂Br₅ NImonoclinic^(e) 4.37^(e) slightly RbSr₂Br₅ 596^(d) monoclinic^(e)4.18^(e) slightly KSr₂I₅ NI monoclinic^(e) 4.39^(e) very NI = noinformation found in the literature; ^(a)data from Bukhalova et al.(1967); ^(b)data from Kellner (1917); ^(c)data from Fink and Seifert(1980); ^(d)data from Riccardi et al. (1970); ^(e)data from Schilling etal. (1996)

Example 2 Moisture Absorption of Scintillator Materials

The tendency for a scintillation material to absorb moisture cansometimes be a limitation to its practical application as a radiationdetector. Moisture absorption of the scintillation materials was studiedat 25° C. using approximately 32 mg amounts of the scintillationmaterials under conditions of 40% relative humidity. FIG. 1 shows themoisture uptake over time of several of the presently disclosedscintillation materials. For comparison, the moisture uptake is alsoprovided for two commonly used metal halide scintillation materials,i.e., NaI:Tl and LaBr₃:Ce 5%. RbSr₂Cl₅:Eu 2.5%, K₂BaBr₄:Eu 5%, KBa₂I₅:Eu2.5%, and K₂BaI₄:Eu 5% were less hygroscopic than NaI:Tl. KSr₂Br₅:Eu2.5%, K₂SrBr₄:Eu 5% and CsSr₂I₅:Eu 2.5% had moisture uptake between thatof LaBr₃:Ce 5% and NaI:Tl.

Example 3 Moisture Absorption of Scintillator Materials

Photoluminescence spectra of the presently disclosed scintillationmaterials were acquired using a Hitachi Fluorescence Spectrophotometer(Hitachi High-Tech Science Corporation, Tokyo, Japan) equipped with aXenon lamp at room temperature. The photoluminescence spectra (see FIGS.2A-2M) are characteristic of divalent Eu luminescence, which completelyinvolves 4f-5d excited states.

Radioluminescence spectra were measured at room temperature undercontinuous irradiation from a Source 1 X-ray generator model CMX003 (32kV and 0.1 mA; Source 1 X-Ray, Campbell, Calif., United States ofAmerica). A model PI Acton Spectra Pro SP-2155 monochromator (PrincetonInstruments, Trenton, N.J., United States of America) was used to recordthe spectra. The single peak emission observed in the radioluminescencespectra shown in FIGS. 3A-3M can be attributed to characteristicemission of Eu²⁺ 5d to 4f transitions, which confirm that Eu ions enterthe metal halide lattice in divalent form.

Absolute light output measurements for the presently disclosedscintillator materials are shown in FIGS. 4A-4M. A Hamamatsu 3177-50photomultiplier tube (PMT; Hamamatsu Photonics, K.K.; Hamamatsu, Japan)was used. Gamma-ray energy spectra were recorded using ¹³⁷Cs as anexcitation source. The measurements were done with the samples coveredand directly coupled to the PMT with mineral oil. A SPECTRALON™(Labsphere, Inc., North Sutton, N.H., United States of America) dome wasused as a reflector. Spectra shown in FIGS. 4A-4M exhibit the positionof the 662 keV gamma-ray photopeak at much higher channel number thanthe reference bismuth germinate (BGO) crystal with its photopeak atchannel 100. The photopeaks were fitted with a Gaussian function todetermine the centroid of the peak. The integral quantum efficiency ofthe PMT according to the emission spectrum of the scintillator was usedto estimate the light output in photons per unit of gamma-ray energy.

The scintillation properties of the presently disclosed ternary metalhalides are summarized in Tables 2 and 3 below. Scintillation decay timewas recorded using a ¹³⁷Cs source and a time-correlated single photoncounting technique. See Bollinger and Thomas (1961). Scintillation decaycurves (fitted with an exponential decay function) for the presentlydisclosed materials are shown in FIGS. 5A-5M.

TABLE 2 Scintillation properties of compounds of formulaA₂B_((1−y))Eu_(y)X₄. Maximum LO RL Scintillation decay Composition(ph/MeV) (nm) (μs) K₂EuCl₄ 23000 475 0.6 (~66%), 3.2 (~25), 0.1K₂Bal₄:Eu 5% 50000 449 0.9 (~68%), 4.2 K₂BaBr₄:Eu 5% 41000 430 0.7(~86%), 2.8 Rb₂BaCl₄:Eu 5% 18000 436 0.7 (~70%), 3.3 K₂SrBr₄:Eu 5% 20000445 0.8 (~97%), 2

TABLE 3 Scintillation properties of compounds of formulaAB_(2(1−y))Eu_(2y)X₅. Maximum LO RL Scintillation decay Composition(ph/MeV) (nm) (μs) RbSr₂Cl₅:Eu 2.5% 32000 426 0.9 (~67%), 1.4 KSr₂Br₅:Eu2.5% 50000 427 0.9 (~92%), 2.6 KBa₂I₅:Eu 2.5% 56000 442 0.9 (~79%), 4.9CsSr₂I₅:Eu 2.5% 50000 441 0.9 (~68%), 4 RbEu₂Cl₅:Eu 2.5% 30000 440 1.8RbBa₂Br₅:Eu 2.5% 29000 425 0.8 (~76%), 3 RbSr₂Br₅:Eu 2.5% 33000 430 0.8KSr₂I₅:Eu 4% 81000 452 0.8

REFERENCES

The references listed below as well as all references cited in thespecification including, but not limited to patents, patent applicationpublications, and journal articles are incorporated herein by referenceto the extent that they supplement, explain, provide a background for,or teach methodology, techniques, and/or compositions employed herein.

-   Bollinger, L. M., and Thomas, G. E.; Review of Scientific    Instruments, 32, 1044-1050 (1961).-   Bukhalova, G. A., and Burlakova, V. M.; Russ. J. Inorg. Chem., 12,    703-705 (1967).-   Fink, H., and Seifert, H.-J.; Anorg. Allg. Chem., 466, 87-96 (1980).-   Kellner, Z.; Anorg. Allg. Chem., 99, 137-183 (1917).-   Korshunov, D. V., et al.; Russ. J. Inorg. Chem., 11, 547-550 (1966).-   Riccardi, R., et al.; Z. Naturforsch, A: Astrophys., Phys. Phys.    Chem., 25, 781-785 (1970);-   Schilling, G., and Meyer, G.; Z. Anorg. Allg. Chem., 622, 759-765    (1996).

It will be understood that various details of the presently disclosedsubject matter may be changed without departing from the scope of thepresently disclosed subject matter. Furthermore, the foregoingdescription is for the purpose of illustration only, and not for thepurpose of limitation.

1-28. (canceled)
 29. A scintillator material comprising Formula (II):AB_(2(1-y))L_(2y)X₅  (II), wherein: 0.0001≦y≦0.5; A is one or morealkali metal; B is one or more alkali earth metal; L is selected fromthe group consisting of Eu, Ce, Tb, Yb, and Pr; and X is a combinationof halides selected from I, F, Cl, and Br.
 30. The scintillator materialof claim 29, wherein A is selected from the group consisting of K, Rband Cs.
 31. A radiation detector comprising a photon detector and ascintillation material, wherein the scintillation material comprises ascintillator material of claim
 29. 32. The radiation detector of claim31, wherein the detector is a medical diagnostic device, a device foroil exploration, or a device for container or baggage scanning.
 33. Amethod of detecting gamma rays, X-rays, cosmic rays, and/or particleshaving an energy of 1 keV or greater, the method comprising using theradiation detector of claim
 31. 34. A method of preparing a scintillatormaterial of claim 29, wherein the method comprises heating a mixture ofraw materials above their respective melting temperatures.
 35. Themethod of claim 34, wherein the method comprises: (a) providing amixture of raw materials, wherein the raw materials are provided in astoichiometric ratio according to Formula (II):AB_(2(1-y))L_(2y)X₅  (II), wherein: 0.0001≦y≦0.5; A is one or morealkali metal; B is one or more alkali earth metal; L is selected fromthe group consisting of Eu, Ce, Tb, Yb, and Pr; and X is a combinationof halides selected from I, F, Cl, and Br; (b) sealing said mixture in asealed container; (c) heating the mixture to about 20° C. above themelting point of the raw material having the highest melting point for aperiod of time; and (d) cooling the mixture to about room temperature.36. The method of claim 35, wherein steps (c) and (d) are repeated oneor more times.
 37. A radiation detector comprising a photon detector anda scintillation material, wherein the scintillation material comprisesFormula (II′):AB_(2(1-z))L_(2z)X₅  (II′), wherein: 0.0001≦z≦1.0; A is one or morealkali metal; B is one or more alkali earth metal; L is selected fromthe group consisting of Eu, Ce, Tb, Yb, and Pr; and X is a combinationof halides selected from I, F, Cl, and Br.
 38. The radiation detector ofclaim 37, wherein A is selected from the group consisting of K, Rb, andCs.
 39. The radiation detector of claim 37, wherein the detector is amedical diagnostic device, a device for oil exploration, or a device forcontainer or baggage scanning.
 40. A method of detecting gamma rays,X-rays, cosmic rays, and/or particles having an energy of 1 keV orgreater, the method comprising using the radiation detector of claim 37.41. A scintillator material comprising Formula (II):AB_(2(1-y))L_(2y)X₅  (II), wherein: 0.0001≦y≦0.5; A is one or morealkali metal; B is one or more alkali earth metal; L is selected fromthe group consisting of Ce, Tb, Yb, and Pr; and X is one or more halide.42. The scintillator material of claim 41, wherein A is selected fromthe group consisting of K, Rb, and Cs.
 43. The scintillator material ofclaim 41, wherein A is K.
 44. The scintillator material of claim 41,wherein B is selected from Sr and Ba.
 45. The scintillator material ofclaim 41, wherein X is selected from the group consisting of I, Cl, andBr.
 46. The scintillator material of claim 41, wherein X is I.
 47. Thescintillator material of claim 41, wherein L is Ce or Pr.
 48. Aradiation detector comprising a photon detector and a scintillationmaterial, wherein the scintillation material comprises a scintillatormaterial of claim
 41. 49. The radiation detector of claim 48, whereinthe detector is a medical diagnostic device, a device for oilexploration, or a device for container or baggage scanning.
 50. A methodof detecting gamma rays, X-rays, cosmic rays, and/or particles having anenergy of 1 keV or greater, the method comprising using the radiationdetector of claim
 48. 51. A method of preparing a scintillator materialof claim 41, wherein the method comprises heating a mixture of rawmaterials above their respective melting temperatures.
 52. The method ofclaim 51, wherein the method comprises: (a) providing a mixture of rawmaterials, wherein the raw materials are provided in a stoichiometricratio according to Formula (II):AB_(2(1-y))L_(2y)X₅  (II), wherein: 0.0001≦y≦0.5; A is one or morealkali metal; B is one or more alkali earth metal; L is selected fromthe group consisting of Ce, Tb, Yb, and Pr; and X is one or more halide;(b) sealing said mixture in a sealed container; (c) heating the mixtureto about 20° C. above the melting point of the raw material having thehighest melting point for a period of time; and (d) cooling the mixtureto about room temperature.
 53. The method of claim 52, wherein steps (c)and (d) are repeated one or more times.
 54. A radiation detectorcomprising a photon detector and a scintillation material, wherein thescintillation material comprises Formula (II′):AB_(2(1-z))L_(2z)X₅  (II′), wherein: 0.0001≦z≦1.0; A is one or morealkali metal; B is one or more alkali earth metal; L is selected fromthe group consisting of Ce, Tb, Yb, and Pr; and X is one or more halide.55. The radiation detector of claim 54, wherein A is selected from thegroup consisting of K, Rb, and Cs.
 56. The radiation detector of claim54, wherein A is K.
 57. The radiation detector of claim 54, wherein B isselected from Sr and Ba.
 58. The radiation detector of claim 54, whereinX is selected from the group consisting of I, Cl, and Br.
 59. Theradiation detector of claim 54, wherein X is I.
 60. The radiationdetector of claim 54, wherein L is Ce or Pr.
 61. The radiation detectorof claim 54, wherein the detector is a medical diagnostic device, adevice for oil exploration, or a device for container or baggagescanning.
 62. A method of detecting gamma rays, X-rays, cosmic rays,and/or particles having an energy of 1 keV or greater, the methodcomprising using the radiation detector of claim 54.